The Taliban use brutality, like amputations and beheadings, to intimidate and expand their power. And they often hold public executions.
Just last month, a Taliban firing squad executed a man and a woman in front of a crowd because the couple had tried to elope - a death penalty offense to the Taliban because the woman was engaged to someone else
In the office on his plane, Couric asked what keeps him up at night.
"I suspect everybody would say the thing that frightens them the most is a group like al Qaeda getting hold of a weapon of mass destruction. And I think that really is a serious worry," Gates said.
"Like a nuclear weapon in Pakistan?" Couric asked.
"Not necessarily from Pakistan. North Korea's another worry," he replied.
During our trip we also stopped in Saudi Arabia. Gates' motorcade took us to see U.S. troops who train the royal family's bodyguards.
Because Gates is the only Bush holdover in the Obama cabinet, he has a unique view of both presidents. But he's extremely reluctant to share his insights.
"You have said that President Obama is more analytical in your view than President Bush," Couric remarked.
"That's something I wished I hadn't said," Gates said.
Asked why, Gates told Couric, "I really have been very disciplined about not drawing those kinds of comparisons."
"What three words would you use to describe President Bush?" Couric asked.
"Committed, questioning, eager to make a decision and move on," Gates said.
The words he used to describe President Obama were "deliberative, decisive and calm."